50W lamp? I would hope this has dusk-dawn control?
Screwfix sell one with adj on/off time light control & PIR sensitivity for £7.50 and you will more likely get a direct replacement as opposed to a cash refund if anything goes wrong.
I think B&Q do them for about £8 too.

Voted cold as it says "splash proof" meaning that if it gets anything more than a light shower over it its going to break or trip the electrics!

Much better to get a recognised one from b&q or screwfix. I have a 100watt one from b&q cost me about £8 ive had it 5yrs now and no problems at all.

I would say splash proof doesn't technically mean anything even your wall mounted shower unit is 'splash proof' (it certainly isn't water proof!) you can only ever go on IP rating - which of course we don't know but I doubt the thing will fill up with water ;-)

The cheap ones in b&q and srewfix (owned by b&q) are similarly rated as IP44

What does IP44 mean?
Protection against water : Protection against water spray.

Definition: Water splashes on to the enclosure from any direction must not have any harmful effects. IP X4

Test conditions: The enclosure is tested by means of a spray head or a flushing pipe which is aimed at it from all sides according to the standardised testing time / volume flow.
Conditions for acceptance: Should water have penetrated, it must not
- be present in quantities which impair the good working order of the operating material or represent a safety hazard;
- deposit on non-conducting parts where it could lead to creep currents;
- come in contact with live parts or coils which are unsuitable for operating in wet conditions;
- collect near the wire end or possibly penetrate the wire.

If you pay more money, you may find a product rated higher such as IP54 or IP65.
An IP54 rating offers dust protection (but not total) and protects against splashing of water but not wash-down, whilst an IP65 product will be fully protected against dust and airborne particles whilst also be protected against water jets which would allow the machine to be washed down.
There are indeed higher ratings still, such as IP68 which would provide complete dust and underwater protection.

You pays your money and takes your choice, but the an IP44 rated product should be suitable for most usual applications unless you plan to submerse it in a fish pond and have it activated everytime the goldfish swim past! :D

Here's the complete codes:

Degrees of Protection - First Digit
The first digit of the IP code indicates the degree that persons are protected against contact with moving parts (other than smooth rotating shafts, etc.) and the degree that equipment is protected against solid foreign bodies intruding into an enclosure.

0 No special protection
1 Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter.
2 Protection against fingers or other object not greater than 80mm in length and 12mm in diameter.
3 Protection from entry by tools, wires, etc., with a diameter of thickness greater than 1.0mm.
4 Protection from entry by solid objects with a diameter or thickness greater than 1.0mm
5 Protection from the amount of dust that would interfere with the operation of the equipment.
6 Dust tight.

Degrees of Protection - Second Digit
The second digit indicates the degree of protection of the equipment inside the enclosure against the harmful entry of various forms of moisture (e.g. dripping, spraying, submersion, etc.)